Biomedical Engineering Reference
In-Depth Information
Appendix C
Some Basic Formulas of Physics (MKS and CGS Units)
Classical Mechanics
Momentum
=
mass
×
velocity,
p
=
mv
units: kgms
-1
;gcms
-1
Kinetic energy,
T
=
=
p
2
/2
m
units: 1 J
=
1kgm
2
s
-2
; 1 erg
=
1gcm
2
s
-2
Force
=
mass
×
acceleration,
F
=
ma
units: 1 N
=
1kgms
-2
;1dyne
=
1gcms
-2
Work
=
force
×
distance
=
change in energy
units: 1 J
=
1Nm
=
1kgm
2
s
-2
; 1 erg
=
1dynecm
=
1gcm
2
s
-2
Impulse
=
force
×
time
=
change in momentum,
I
=
Ft
=
p
units: 1 N s = 1kgms
-1
;1dynes= 1gcms
-1
Angular momentum, uniform circular motion,
L
1
2
mv
2
=
mvr
1 erg s
Centripetal acceleration, uniform circular motion,
a
units: 1 kgm
2
s
-1
1 Js;1gcm
2
s
-1
=
=
v
2
/
r
=
units: ms
-2
;cms
-2
Relativistic Mechanics (units same as in classical mechanics)
Relativistic quantities:
v
=
speed
of object
speed of light in vacuum
c
=
v
/
c
,
dimen
sionless, 0
β
=
≤
β
<1
1/
1-
2
, dimensionless, 1
γ =
β
≤ γ
<
∞
Rest energy,
E
0
=
mc
2
,
m
rest mass
=
Relativistic mass,
m
/
1-
2
β
= γ
m
mc
2
/
1-
Total energy,
E
T
=
mc
2
Kinetic energy
=
total energy—rest energy,
T
=
E
T
-
E
0
=
mc
2
(γ -1)=
mc
2
β
2
= γ
2
-1
1
1-
β
mv
/
1-
Momentum,
p
= γ
mv
=
β
2
